Back to EveryPatent.com
United States Patent |
6,023,375
|
Kreitzer
|
February 8, 2000
|
Projection lenses for use with large pixelized panels
Abstract
A projection lens for use with LCD panels is provided. The lens has a first
lens unit which has a positive power and a second lens unit which has a
negative power. The first lens unit contains at least four lens elements,
namely, a positive first lens element, a negative second lens element
which is composed of a high dispersion material, a third lens element of
weak optical power, and a positive fourth lens element of strong optical
power. The projection lens achieves a correction of chromatic aberration
on the order of about a quarter of pixel for large LCD panels having
pixels on the order of 200 microns.
Inventors:
|
Kreitzer; Melvyn H. (Cincinnati, OH)
|
Assignee:
|
U.S. Precision Lens Inc. (Cincinnati, OH)
|
Appl. No.:
|
908115 |
Filed:
|
August 11, 1997 |
Current U.S. Class: |
359/649; 359/713; 359/714; 359/757; 359/764 |
Intern'l Class: |
G02B 013/18; G02B 009/60; G02B 009/62 |
Field of Search: |
359/648,649,650,651,757,764,708,713,714
|
References Cited
U.S. Patent Documents
2468564 | Apr., 1949 | Luneburg.
| |
4189211 | Feb., 1980 | Taylor.
| |
4425028 | Jan., 1984 | Gagnon et al.
| |
4461542 | Jul., 1984 | Gagnon.
| |
4526442 | Jul., 1985 | Betensky.
| |
4548480 | Oct., 1985 | Yamamoto et al.
| |
4564269 | Jan., 1986 | Uehara.
| |
4682862 | Jul., 1987 | Moskovich.
| |
4704009 | Nov., 1987 | Yamamoto et al.
| |
4776681 | Oct., 1988 | Moskovich.
| |
4826311 | May., 1989 | Ledebuhr.
| |
4838667 | Jun., 1989 | Ueda.
| |
4900139 | Feb., 1990 | Kreitzer.
| |
4963007 | Oct., 1990 | Moskovich | 359/649.
|
5042929 | Aug., 1991 | Tanaka et al.
| |
5179473 | Jan., 1993 | Yano et al.
| |
5200861 | Apr., 1993 | Moskovich.
| |
5218480 | Jun., 1993 | Moskovich.
| |
5278698 | Jan., 1994 | Iizuka et al.
| |
5309283 | May., 1994 | Kreitzer.
| |
5313330 | May., 1994 | Betensky.
| |
5329363 | Jul., 1994 | Moskovich.
| |
5331462 | Jul., 1994 | Yano.
| |
5353161 | Oct., 1994 | Ono.
| |
5442484 | Aug., 1995 | Shikawa.
| |
5455713 | Oct., 1995 | Kreitzer.
| |
5493446 | Feb., 1996 | Nakajima.
| |
5625495 | Apr., 1997 | Moskovich.
| |
5659424 | Aug., 1997 | Osawa et al.
| |
5808804 | Sep., 1998 | Moskovich | 359/649.
|
5822129 | Oct., 1998 | Sekine | 359/649.
|
Foreign Patent Documents |
311116 | Dec., 1989 | EP.
| |
61-205909 | Dec., 1986 | JP.
| |
WO97/41461 | Nov., 1997 | WO.
| |
Other References
The Handbook of Plastic Optics, U.S. Precision Lens, Inc., Cincinnati,
Ohio, 1983, pp. 17-29.
|
Primary Examiner: Sugarman; Scott J.
Attorney, Agent or Firm: Klee; Maurice M.
Parent Case Text
CROSS REFERENCE TO RELATED PROVISIONAL APPLICATION
This application claims the benefit under 35 USC .sctn.119(e) of U.S.
Provisional Applications Serial Nos. 60/024,083 filed Aug. 16, 1996 and
60/037,266 filed Jan. 31, 1997.
Claims
What is claimed is:
1. A projection lens for forming an image of an object, said lens
consisting in order from its image end to its object end of:
(A) a first lens unit having a positive power and comprising in order from
the image side to the object side:
(i) a positive lens element;
(ii) a negative lens element;
(iii) a lens element of weak optical power; and
(iv) a positive lens element of strong optical power; and
(B) a second lens unit having a negative power; wherein:
(a) the first lens unit and the second lens unit have a combined optical
power P.sub.0 ;
(b) the positive lens element of strong optical power has a power P.sub.E4
; and
(C) P.sub.E4 >1.5.multidot.P.sub.0.
2. A projection lens system for forming an image of an object, said system
comprising:
(a) an illumination system comprising a light source and illumination
optics which forms an image of the light source, said image of the light
source being the output of the illumination system;
(b) a pixelized panel which comprises the object; and
(c) a projection lens which forms the image of the object, said lens
comprising in order from its image end to its object end:
(A) a first lens unit having a positive power and comprising in order from
the image side to the object side:
(i) a positive lens element;
(ii) a negative lens element;
(iii) a lens element of weak optical power; and
(iv) a positive lens element of strong optical power; and
(B) a second lens unit having a negative power.
3. The projection lens system of claim 2 wherein said projection lens has
an entrance pupil whose location substantially corresponds to the location
of the output of the illumination system.
4. The projection lens system of claim 2 further comprising a field lens
between the pixelized panel and the projection lens.
5. A projection lens for forming an image of an object, said lens
consisting in order from its image end to its object end of:
(A) a first lens unit having a positive power and comprising in order from
the image side to the object side:
(i) a positive lens element;
(ii) a negative lens element;
(iii) a lens element of weak optical power; and
(iv) a positive lens element of strong optical power; and
(B) a second lens unit having a negative power;
wherein the lens has a distortion which is less than about one percent at
the image.
6. A projection lens for forming an image of an object, said lens
consisting in order from its image end to its object end of:
(A) a first lens unit having a positive power and consisting in order from
the image side to the object side of:
(i) a positive lens element;
(ii) a negative lens element;
(iii) a lens element of weak optical power; and
(iv) a positive lens element of strong optical power; and
(B) a second lens unit having a negative power.
7. The projection lens of claim 1, 5, or 6 wherein the negative lens
element of the first lens unit is composed of a high dispersion material.
8. The projection lens of claim 1, 5, or 6 wherein the second lens unit is
a singlet.
9. The projection lens of claim 1, 5, or 6 wherein the second lens unit
comprises two lens elements, one having a positive power and the other a
negative power.
10. The projection lens of claim 1, 5, or 6 wherein each of the first and
second lens units comprises at least one aspheric surface.
11. The projection lens of claim 1, 5, or 6 wherein the modulation transfer
function of the lens at 5 cycles/millimeter changes less than about ten
percent as the lens is heated from room temperature to its operating
temperature.
12. The projection lens of claim 1 or 6 wherein the lens has a distortion
which is less than about one percent at the image.
13. The projection lens of claim 1, 5, or 6 wherein the object is a
pixelized panel.
14. The projection lens of claim 13 wherein the projection lens has a
lateral color aberration which is less than about a pixel at the object.
15. A projection lens system for forming an image of an object, said system
comprising:
(a) an illumination system comprising a light source and illumination
optics which forms an image of the light source, said image of the light
source being the output of the illumination system;
(b) a pixelized panel which comprises the object; and
(c) the projection lens of claim 1, 5, or 6.
16. The projection lens system of claim 15 wherein said projection lens has
an entrance pupil whose location substantially corresponds to the location
of the output of the illumination system.
17. The projection lens system of claim 15 further comprising a field lens
between the pixelized panel and the projection lens.
18. The projection lens of claim 6 wherein the lens has a distortion which
is less than about one percent at the image.
19. A projection lens system for forming an image of an object, said system
comprising:
(a) an illumination system comprising a light source and illumination
optics which forms an image of the light source, said image of the light
source being the output of the illumination system;
(b) a pixelized panel which comprises the object; and
(c) a projection lens which forms the image of the object, said lens
consisting in order from its image end to its object end of:
(A) a first lens unit having a positive power and comprising in order from
the image side to the object side:
(i) a positive lens element;
(ii) a negative lens element;
(iii) a lens element of weak optical power; and
(iv) a positive lens element of strong optical power; and
(B) a second lens unit having a negative power.
20. The projection lens system of claim 19 further comprising a field lens
between the pixelized panel and the projection lens.
21. The projection lens system of claim 19 wherein said projection lens has
an entrance pupil whose location substantially corresponds to the location
of the output of the illumination system.
Description
FIELD OF THE INVENTION
This invention relates to projection lenses and, in particular, to
projection lenses which can be used, inter alia, to form an image of an
object composed of pixels, e.g., a LCD.
BACKGROUND OF THE INVENTION
Projection lens systems (also referred to herein as "projection systems")
are used to form an image of an object on a viewing screen. The basic
structure of such a system is shown in FIG. 4, wherein 10 is a light
source (e.g., a tungsten-halogen lamp), 12 is illumination optics which
forms an image of the light source (hereinafter referred to as the
"output" of the illumination system), 14 is the object which is to be
projected (e.g., a LCD matrix of on and off pixels), and 13 is a
projection lens, composed of multiple lens elements, which forms an
enlarged image of object 14 on viewing screen 16. The system can also
include a field lens, e.g., a Fresnel lens, in the vicinity of the
pixelized panel to appropriately locate the exit pupil of the illumination
system.
Projection lens systems in which the object is a pixelized panel are used
in a variety of applications, including data display systems. Such
projection lens systems preferably employ a single projection lens which
forms an image of, for example, a single panel having red, green, and blue
pixels.
Pixelized panels, specifically, LCD panels, come in various sizes depending
upon the type of projection system in which they are to be used. Large LCD
panels, e.g., panels having a diagonal of about 10.6 inches (about 270
millimeters), can be effectively employed in producing high resolution
color images since such panels can have a high pixel count while still
maintaining a pixel size which is large enough for reliable manufacture.
In this regard, it should be noted that for a full color image from a
single LCD panel, the number of pixels needed is three times that required
for a monochrome image, thus making for small pixel sizes unless large LCD
panels are used.
There exists a need in the art for a projection lens for use with a large
pixelized panel which simultaneously has at least the following
properties: (1) a long focal length; (2) the ability to operate at various
magnifications while maintaining an efficient coupling to the output of
the illumination system and a high level of aberration correction; (3) a
relatively small size, including a relatively small number of lens
elements, a relatively small barrel length, and a relatively small maximum
lens diameter; (4) a high level of color correction; (5) low distortion;
and (6) low sensitivity to temperature changes.
For a large pixelized panel, the use of a long focal length allows the
field of view of the projection lens to be maintained in a range which
facilitates aberration correction, e.g., the semi field of view of the
lens can be around 25.degree..
A projection lens which can efficiently operate at various magnifications
is desirable since it allows the projection system to be used with screens
of different sizes and halls of different dimensions without the need to
change any of the components of the system. Only the object and image
conjugates need to be changed which can be readily accomplished by moving
the lens relative to the pixelized panel. The challenge, of course, is to
provide efficient coupling to the output of the illumination system and a
high level of aberration correction throughout the operative range of
magnifications.
A relatively small projection lens is desirable from a cost, weight, and
size point of view. Large numbers of lens elements and elements having
large diameters consume more raw materials, weigh more, and are more
expensive to build and mount. Long barrel lengths normally increase the
overall size of the projection system, which again leads to increased cost
and weight. Accordingly, a lens with a minimum number of relatively small
lens elements, located relatively close to one another, is desired.
A high level of color correction is important because color aberrations can
be easily seen in the image of a pixelized panel as a smudging of a pixel
or, in extreme cases, the complete dropping of a pixel from the image.
These problems are typically most severe at the edges of the field. In
general terms, the color correction, as measured at the pixelized panel,
should be better than about a pixel and, preferably, better than about a
half a pixel to avoid these problems.
All of the chromatic aberrations of the system need to be addressed, with
lateral color, chromatic variation of coma, and chromatic aberration of
astigmatism typically being most challenging. Lateral color, i.e., the
variation of magnification with color, is particularly troublesome since
it manifests itself as a decrease in contrast, especially at the edges of
the field. In extreme cases, a rainbow effect in the region of the full
field can be seen.
In projection systems employing cathode ray tubes (CRTs) a small amount of
(residual) lateral color can be compensated for electronically by, for
example, reducing the size of the image produced on the face of the red
CRT relative to that produced on the blue CRT. With a pixelized panel,
however, such an accommodation cannot be performed because the image is
digitized and thus a smooth adjustment in size across the full field of
view is not possible. A higher level of lateral color correction is thus
needed from the projection lens.
It should be noted that color aberrations become more difficult to correct
as the focal length of the projection lens increases. Thus, the first and
fourth criteria discussed above, i.e., a long focal length and a high
level of color correction, work against one another in arriving at a
suitable lens design.
The use of a pixelized panel to display data leads to stringent
requirements regarding the correction of distortion. This is so because
good image quality is required even at the extreme points of the field of
view of the lens when viewing data. As will be evident, an undistorted
image of a displayed number or letter is just as important at the edge of
the field as it is at the center. Moreover, projection lenses are often
used with offset panels, the lenses of FIGS. 1-3 being designed for such
use. In such a case, the distortion at the viewing screen does not vary
symmetrically about a horizontal line through the center of the screen but
can increase monotonically from, for example, the bottom to the top of the
screen. This effect makes even a small amount of distortion readily
visible to the viewer.
In order to produce an image of sufficient brightness, a substantial amount
of light must pass through the projection lens. As a result, a significant
temperature difference normally exists between room temperature and the
lens' operating temperature. In addition, the lens needs to be able to
operate under a variety of environmental conditions. For example,
projection lens systems are often mounted to the ceiling of a room, which
may comprise the roof of a building where the ambient temperature can be
substantially above 40.degree. C. To address these effects, a projection
lens whose optical properties are relatively insensitivity to temperature
changes is needed.
One way to address the temperature sensitivity problem is to use lens
elements composed of glass. Compared to plastic, the radii of curvature
and the index of refraction of a glass element generally change less than
those of a plastic element. However, glass elements are generally more
expensive than plastic elements, especially if aspherical surfaces are
needed for aberration control. As described below, plastic elements can be
used and temperature insensitivity still achieved provided the powers and
locations of the plastic elements are properly chosen.
The projection lenses described below achieve all of the above requirements
and can be successfully used in producing relatively low cost projection
lens systems capable of forming a high quality color image of a pixelized
panel on a viewing screen.
DESCRIPTION OF THE PRIOR ART
Projection lenses for use with pixelized panels are described in various
patents including Taylor, U.S. Pat. No. 4,189,211, Tanaka et al., U.S.
Pat. No. 5,042,929, Yano et al., U.S. Pat. No. 5,179,473, Moskovich, U.S.
Pat. No. 5,200,861, Moskovich, U.S. Pat. No. 5,218,480, Iizuka et al.,
U.S. Pat. No. 5,278,698, Betensky, U.S. Pat. No. 5,313,330, and Yano, U.S.
Pat. No. 5,331,462.
Discussions of LCD systems can be found in Gagnon et al., U.S. Pat. No.
4,425,028, Gagnon, U.S. Pat. No. 4,461,542, Ledebuhr, U.S. Pat. No.
4,826,311, and EPO Patent Publication No. 311,116.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to
provide improved projection lenses for use with a pixelized panel which
simultaneously have each of the six desired properties discussed above.
This object is achieved by means of a projection lens which comprises in
order from its image side to its object side (i.e., from its long
conjugate side to its short conjugate side):
(A) a first lens unit having a positive power and comprising in order from
the image side to the object side:
(i) a positive lens element;
(ii) a negative lens element;
(iii) a lens element of weak power, e.g., a power which is less than about
50 percent of the overall power of the projection lens; and
(iv) a positive lens element of strong power, e.g., a power which is at
least about 150 percent of the overall power of the projection lens; and
(B) a second lens unit having a negative power.
In certain embodiments, the second lens unit is a singlet (see FIGS. 1 and
2), while in other embodiments, it comprises two lens elements, one having
a positive power and the other a negative power (see FIG. 3).
The projection lenses of the invention are preferably designed using the
location of the output of the illumination system as a pseudo-aperture
stop/entrance pupil of the projection lens (see Betensky, U.S. Pat. No.
5,313,330, the relevant portions of which are incorporated herein by
reference). In this way, efficient coupling is achieved between the light
output of the illumination system and the projection lens.
In accordance with these embodiments, the invention provides a projection
lens system which forms an image of an object and comprises:
(a) an illumination system comprising a light source and illumination
optics which forms an image of the light source, said image being the
output of the illumination system;
(b) a pixelized panel which comprises the object; and
(c) a projection lens of the type described above, said projection lens
having an entrance pupil whose location substantially corresponds to the
location of the output of the illumination system.
In some embodiments of the invention, zooming of the projection lens system
is achieved, by varying: (a) the distance between the projection lens and
the pixelized panel; and (b) the distance between the first lens unit and
the second lens unit. Zooming on the order of 5% can be achieved in this
way. The lens system of FIG. 3 is of this type.
In other embodiments, focusing of the projection lens system is achieved by
varying: (a) the distance between the projection lens and the pixelized
panel: and (b) the distance between the first and second lens elements of
the first lens unit. The lens systems of FIGS. 1 and 2 are of this type.
The projection lenses of the invention are also designed to be
substantially athermal. As discussed fully below, this is done by
balancing the powers of the plastic lens elements having substantial
optical power. In this way, changes in the power of the positive lens
elements caused by temperature changes are compensated for by changes in
the power of the negative lens elements, thus providing substantially
constant overall optical properties for the projection lens as its
temperature changes.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A, 2A, and 3A are schematic side views of projection lenses
constructed in accordance with the invention.
FIGS. 1B, 2B, and 3B show the projection lenses of FIGS. 1A, 2A, and 3A,
respectively, in combination with a pixelized panel (PP) and a Fresnel
lens (FL).
FIG. 4 is a schematic diagram showing an overall projection lens system in
which the projection lens of the present invention can be used.
The foregoing drawings, which are incorporated in and constitute part of
the specification, illustrate the preferred embodiments of the invention,
and together with the description, serve to explain the principles of the
invention. It is to be understood, of course, that both the drawings and
the description are explanatory only and are not restrictive of the
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The projection lenses of the present invention have the general form of a
positive first lens unit and a negative second lens unit. Each of the two
units includes at least one aspheric surface for use in aberration
correction, including correction of spherical aberration, astigmatism,
coma, and distortion. As discussed above, the system's distortion needs to
be highly corrected for lens systems used with pixelized panels. The
distortion correction is generally better than about one percent at the
image, and preferably better than about 0.5 percent.
For purposes of color correction, the first lens unit includes a negative
lens element composed of a high dispersion material and at least one
positive lens element composed of a low dispersion material. The high and
low dispersion materials can be glass or plastic.
In general terms, a high dispersion material is a material having a
dispersion like flint glass and a low dispersion material is a material
having a dispersion like crown glass. More particularly, high dispersion
materials are those having V-values ranging from 20 to 50 for an index of
refraction in the range from 1.85 to 1.5, respectively, and low dispersion
materials are those having V-values ranging from 35 to 75 for the same
range of indices of refraction.
For plastic lens elements, the high and low dispersion materials can be
styrene and acrylic, respectively. Other plastics can, of course, be used
if desired. For example, in place of styrene, polycarbonates and
copolymers of polystyrene and acrylic (e.g., NAS) having flint-like
dispersions can be used. See The Handbook of Plastic Optics, U.S.
Precision Lens, Inc., Cincinnati, Ohio, 1983, pages 17-29.
As discussed above, the projection lenses of the invention are athermalized
so that the optical performance of the system does not substantially
change as the projection lens is heated from room temperature to its
operating temperature. More specifically, the thermally-induced change in
the modulation transfer function of the system at, for example, 5
cycles/millimeter, is preferably less than about 10%. The desired thermal
stabilization is achieved through the selection and placement in the lens
of the plastic lens elements.
Ordinarily, the use of plastic lens elements has the drawback that the
refractive index of plastic optical materials changes significantly with
temperature. Another effect is the change in shape, i.e., expansion or
contraction, of plastic optical materials with temperature. This latter
effect is usually less significant than the change in index of refraction.
If only low power plastic lens elements are used in a lens it is possible
to achieve a balance between the thermal changes in the plastic optics and
the thermal changes in the plastic or aluminum mechanical components of
the system, e.g., the lens barrel which is usually the major mechanical
source of thermally-caused focus changes. The unrestricted use of optical
plastics in a design, i.e., the ability to use plastic lens elements of
relatively high power, has advantages in that, since the plastic lens
elements can be readily molded, non-spherical optical surfaces (aspherics)
can be used to maximize the capability (performance) of a particular lens
design. The use of relatively high power plastic elements also leads to a
lens having an overall lower cost.
If the net plastic optical power in a design is significant, then
athermalization needs to be performed or the focus of the lens will change
significantly as the lens' temperature changes from room temperature to
its operating temperature. This is especially so with projectors which
must transmit significant amounts of light to a viewing screen and thus
have an operating temperature significantly above room temperature.
For the projection lenses of the present invention, athermalization is
achieved by balancing positive and negative plastic optical power, while
also taking into account both the location of the plastic lens elements
and the marginal ray heights at those elements.
The location of the plastic lens elements is significant in terms of the
amount of temperature change the element will undergo and thus the amount
of change which will occur in the element's index of refraction. In
general, elements close to the light source or the image of the light
source will undergo greater temperature changes. In practice, a
temperature distribution in the region where the projection lens is to be
located is measured with the light source and its associated illumination
optics operating and those measured values are used in the design of the
projection lens.
The marginal ray height at a particular plastic lens element determines,
for a given thermal change, whether changes in the element's index of
refraction will be significant with regard to the overall thermal
stability of the lens. Elements for which the marginal ray height is
small, e.g., elements near the focus of the system, will in general have
less effect on the overall thermal stability of the system than elements
for which the marginal ray height is large.
Based on the foregoing considerations, athermalization is achieved by
balancing the amount of negative and positive power in the plastic lens
elements with the contributions of particular elements being adjusted
based on the temperature change which the element is expected to undergo
and the marginal ray height at the element. In practice, this
athermalization procedure is incorporated into a computerized lens design
program as follows. First, a ray trace is performed at a first temperature
distribution and a back focal distance is calculated. The ray trace can be
a paraxial ray trace for the marginal ray. Second, the same ray trace is
performed at a second temperature distribution and the back focal distance
is again calculated. Neither the first nor the second temperature
distribution need be constant over the entire lens but can, and in the
typical case does, vary from lens element to lens element. The calculated
back focal distances are then constrained to a constant value as the
design of the system is optimized using the lens design program.
It should be noted that the foregoing approach assumes that the mechanical
mounts for the projection lens and the pixelized panel hold the distance
between the last lens surface and the panel substantially constant as the
temperature of the system changes. If such an assumption is not warranted,
other provisions can be made for performing the athermalization, e.g., a
measured value for the relative movement of the mechanical mounts can be
included in the process or an alternate distance, e.g., the distance
between the front lens surface and the panel, can be assumed to be
mechanically fixed.
FIGS. 1 to 3 illustrate various projection lenses constructed in accordance
with the invention. Corresponding prescriptions and optical properties
appear in Tables 1 to 3, respectively. HOYA or SCHOTT designations are
used for the glasses employed in the lens systems. Equivalent glasses made
by other manufacturers can be used in the practice of the invention.
Industry acceptable materials are used for the plastic elements.
The aspheric coefficients set forth in the tables are for use in the
following equation:
##EQU1##
where z is the surface sag at a distance y from the optical axis of the
system, c is the curvature of the lens at the optical axis, and k is a
conic constant, which is zero except where indicated in the prescriptions
of Tables 1-3.
The abbreviations used in the tables are as follows:
______________________________________
EFL effective focal length
FVD front vertex distance
f/ f-number
ENP entrance pupil as seen from
the long conjugate
BRL barrel length
OBJ HT object height
MAG magnification
STOP location and size of
aperture stop
IMD image distance
OBD object distance
OVL overall length.
______________________________________
The values for these parameters reported in Tables 1-3 were calculated with
the Fresnel lens as part of the system. The designation "a" associated
with various surfaces in the tables represents an aspheric surface., i.e.,
a surface for which at least one of D, E, F, G, H, or I in the above
equation is not zero. All dimensions given in the tables are in
millimeters. The tables are constructed on the assumption that light
travels from left to right in the figures. In actual practice, the viewing
screen will be on the left and the pixelized panel will be on the right,
and light will travel from right to left. The pixelized panel is shown in
FIGS. 1B, 2B, and 3B by the designation "PP" and the Fresnel lens
associated with the pixelized panel is shown by the designation "FL".
In Tables 1 and 2, the first lens unit (U1) comprises surfaces 1-8 and the
second lens unit (U2) comprises surfaces 9-10. In Table 3, the first lens
unit (U1) comprises surfaces 2-9 and the second lens unit (U2) comprises
surfaces 10-13. Surface 1 in Table 3 is an optional vignetting surface.
As discussed above, the projection lenses of FIGS. 1-3 were designed using
the pseudo-aperture stop/entrance pupil technique of Betensky, U.S. Pat.
No. 5,313,330. In accordance with this approach, the illumination system
is used to define the entrance pupil for the projection lens, with the
entrance pupil being located at a constant position relative to the
pixelized panel for all lens focal lengths and conjugates. The location of
this pupil is determined by the substantially parallel light
(substantially telecentric light) which passes through the pixelized panel
from the illumination system and the Fresnel lens which is located at a
fixed position on the projection lens side of the panel.
Surfaces 11 in Tables 1 and 2, and surface 14 in Table 3, constitute the
pseudo-aperture stop of the above Betensky patent. Its location
corresponds to the location of the output of the illumination system. As
can be seen in the subtables labeled "Variable Spaces," the distance from
the pseudo-aperture stop to the pixelized panel is essentially constant
for all focal positions/zoom positions (magnifications) of the projection
lens systems of FIGS. 1-3 (see the column labeled "Image Distance"). In
contrast, "Space 2" changes for the different magnifications. For the
focus positions shown, this space is negative corresponding to the
illumination output being located within the space defined by the lens'
front and back lens surfaces.
As also discussed above, the projection lenses of FIGS. 1-2 can be focused
over a large conjugate range by varying the distance between the first and
second lens elements of the first lens unit in conjunction with moving the
entire lens relative to the pixelized panel. As shown in Tables 1-2, the
amount of movement between these lens elements is small, e.g., less than
about 1 millimeter.
For the lens system of FIG. 3, zooming is achieved by varying the distance
between the first and second lens units, again in conjunction with the
motion of the whole lens. As shown in Table 3, the movement of the first
lens unit relative to the second lens unit is small compared to the
overall movement of the lens system relative to the pixelized panel.
Table 4 summarizes various properties of the lens systems of the invention,
where P.sub.0 is the overall power of the lens system excluding the
Fresnel lens, P.sub.U1 is the power of the first lens unit and is positive
in all cases, P.sub.U2 is the power of the second lens unit and is
negative in all cases, P.sub.E3 is the power of the third lens element and
is less than about 50 percent of P.sub.0 in all cases, and P.sub.E4 is the
power of the fourth lens element and is greater than about 150 percent of
P.sub.0 in all cases. It should also be noted that a preferred value for
the ratio of P.sub.U1 /P.sub.0 is greater than about 1.3 and for the ratio
of .vertline.P.sub.U2 .vertline./P.sub.0 is greater than about 0.6. As
shown in Table 4, the lens systems of FIGS. 1-3 achieve these preferred
ratios.
The lenses of FIGS. 1-3 were designed for use with LCD panels having a
diagonal of about 10.6 inches (about 270 millimeters), which corresponds
to an effective diagonal of approximately 12.2 inches (approximately 310
millimeters) when the offset of the panel from the lens system's optical
axis is included. The panels have a pixel size of 200 microns,
corresponding to over 1,000 TV lines of horizontal resolution. The images
of the panels produced by the lenses of the invention typically range from
about 60 inches (about 1,525 millimeters) to about 250 inches (about 6,350
millimeters). Significantly, the lenses achieve extremely good chromatic
correction to the order of a quarter pixel (50 microns) or less. This is
an extremely important feature for high quality data or video projection.
Although specific embodiments of the invention have been described and
illustrated, it is to be understood that a variety of modifications which
do not depart from the scope and spirit of the invention will be evident
to persons of ordinary skill in the art from the foregoing disclosure.
TABLE 1
__________________________________________________________________________
Surf. Clear Aperture
No. Type Radius Thickness Glass Diameter
__________________________________________________________________________
1 80.2345
13.60000 BACD18
91.61
2 189.5129
Space 1 89.35
3 a -363.9135
8.71000 STYRENE
87.86
4 ac 128.5309
20.04798 83.57
5 ac 335.8461
12.44000 ACRYLIC
87.46
6 a 1374.9859
1.46824 88.46
7 ac 121.3770
24.04000 ACRYLIC
87.21
8 a -180.9905
36.06222 87.18
9 a -58.6444
8.71000 ACRYLIC
88.41
10 a -146.2454
Space 2 105.89
11 Aperture stop
278.00000 72.07
12 .infin.
2.00000 ACRYLIC
303.99
13 acf -145.1760
Image distance 305.15
__________________________________________________________________________
Symbol Description
a -- Polynomial asphere
c -- Conic section
f -- Fresnel
__________________________________________________________________________
Conics
Surface
Number
Constant
__________________________________________________________________________
4 5.0000E-01
5 2.0000E+01
7 -1.8000E+00
13 -1.0000E+00
__________________________________________________________________________
Even Polynomial Aspheres
Surf.
No.
D E F G H I
__________________________________________________________________________
3 2.5865E-08
4.6778E-11
-3.2126E-14
6.7943E-18
2.2478E-21
-1.0837E-24
4 1.8487E-07
8.5854E-11
1.5067E-14
-1.0392E-17
1.2111E-20
-2.3976E-24
5 2.5567E-08
-5.6794E-11
-1.0633E-14
1.2259E-18
-1.8325E-22
-9.9762E-25
6 -5.0030E-07
-1.5892E-10
4.7261E-15
-3.4141E-18
-1.1894E-21
-2.7529E-26
7 -2.4788E-07
-3.3215E-11
-1.5518E-14
1.6811E-18
-5.1058E-22
-1.1613E-24
8 -1.4800E-07
-5.8020E-11
-6.5836E-15
-8.4681E-18
-1.9423E-21
1.6749E-26
9 -6.3747E-07
6.9165E-11
2.5912E-14
1.5153E-17
-1.5001E-20
3.9065E-24
10 -2.7228E-07
1.7843E-10
-1.2246E-14
-1.7512E-18
-2.1004E-23
5.3283E-26
13 -3.5550E-09
1.5454E-14
-4.2142E-20
0.0000E+00
0.0000E+00
0.0000E+00
__________________________________________________________________________
Variable Spaces
Focus Space 1
Space 2 Focal
Image
Pos. T(2)
T(10) Shift
Distance
__________________________________________________________________________
1 10.566
-68.357 -0.894
10.006
2 10.007
-89.647 -0.285
10.021
3 10.817
-53.005 -1.586
10.006
__________________________________________________________________________
SYSTEM FIRST ORDER PROPERTIES, POS 1
OBJ. HT:
-1370.0 f/ 3.93 MAG:
-0.1100
STOP: 0.00 after surface 11.
DIA:
71.702
EFL: 350.123 FVD:
357.293
ENP:
35.8909
IMD: 10.0058 BRL:
347.287
OBD: -3169.06 OVL:
3526.35
SYSTEM FIRST ORDER PROPERTIES, POS 2
OBJ. HT:
-3750.0 f/ 3.93 MAG:
-0.0400
STOP: 0.00 after surface 11.
DIA:
71.734
EFL: 323.586 FVD:
335.459
ENP:
4.10812
IMD: 10.0205 BRL:
325.439
OBD: -8104.27 OVL:
8439.73
SYSTEM FIRST ORDER PROPERTIES, POS 3
OBJ. HT:
-935.00 f/ 4.02 MAG:
-0.1600
STOP: 0.00 after surface 11.
DIA:
70.033
EFL: 371.879 FVD:
372.896
ENP:
62.2578
IMD: 10.0061 BRL:
362.890
OBD: -2286.90 OVL:
2659.80
__________________________________________________________________________
First Order Properties of Elements
Element Surface
Number Numbers Power f'
__________________________________________________________________________
1 1 2 0.48329E-02
206.92
2 3 4 -0.63050E-02
-158.60
3 5 6 0.11155E-02
896.44
4 7 8 0.66177E-02
151.11
5 9 10 -0.48777E-02
-205.01
6 12 13 0.34012E-02
294.01
__________________________________________________________________________
TABLE 2
__________________________________________________________________________
Surf. Clear Aperture
No. Type Radius Thickness Glass Diameter
__________________________________________________________________________
1 80.2345
13.60000 BACD18
91.70
2 189.5129
Space 1 89.40
3 a -350.9185
8.71000 STYRENE
86.28
4 ac 128.9831
20.50230 82.25
5 ac 335.8461
12.44000 ACRYLIC
87.50
6 a 1374.9859
1.46824 88.50
7 ac 121.3770
24.04000 ACRYLIC
87.30
8 a -180.9905
36.06000 87.20
9 a -57.9805
8.71000 ACRYLIC
88.84
10 a -136.8970
Space 2 105.83
11 Aperture stop
278.00000 72.10
12 .infin.
2.00000 ACRYLIC
304.00
13 acf -145.1760
Image distance 305.20
__________________________________________________________________________
Symbol Description
a -- Polynomial asphere
c -- Conic section
f -- Fresnel
__________________________________________________________________________
Conics
Surface
Number
Constant
__________________________________________________________________________
4 5.0000E-01
5 2.0000E+01
7 -1.8000E+00
13 -1.0000E+00
__________________________________________________________________________
Even Polynomial Aspheres
Surf.
No.
D E F G H I
__________________________________________________________________________
3 1.7590E-08
5.0387E-11
-3.3204E-14
7.6014E-18
2.2646E-21
-1.2446E-24
4 1.6747E-07
8.4654E-11
1.7954E-14
-1.0849E-17
1.2013E-20
-2.5146E-24
5 2.5567E-08
-5.6794E-11
-1.0633E-14
1.2259E-18
-1.8325E-22
-9.9762E-25
6 -5.0030E-07
-1.5892E-10
4.7261E-15
-3.4141E-18
-1.1894E-21
-2.7529E-26
7 -2.4788E-07
-3.3215E-11
-1.5518E-14
1.6811E-18
-5.1058E-22
-1.1613E-24
8 -1.4800E-07
-5.8020E-11
-6.5836E-i5
-8.4681E-18
-1.9423E-21
1.6749E-26
9 -7.1616E-07
5.7268E-11
5.0760E-14
1.3376E-17
-1.6262E-20
4.2647E-24
10 -3.6370E-07
1.9830E-10
-1.0978E-14
-1.4929E-18
-2.8229E-22
7.7082E-26
13 -3.5550E-09
1.5454E-14
-4.2142E-20
0.0000E+00
0.0000E+00
0.0000E+00
__________________________________________________________________________
Variable Spaces
Focus Space 1
Space 2 Focal
Image
Pos. T(2)
T(10) Shift
Distance
__________________________________________________________________________
1 10.566
-70.095 -1.230
9.995
2 10.007
-91.034 -0.494
10.009
3 10.817
-55.028 -2.053
9.997
__________________________________________________________________________
SYSTEM FIRST ORDER PROPERTIES, POS 1
OBJ. HT:
-1370.0 f/ 3.93 MAG:
-0.1100
STOP: 0.00 after surface 11.
DIA:
71.697
EFL: 344.980 FVD:
355.996
ENP:
34.9155
IMD: 9.99523 BRL:
346.001
OBD: -3122.63 OVL:
3478.62
SYSTEM FIRST ORDER PROPERTIES, POS 2
OBJ. HT:
-3750.0 f/ 3.93 MAG:
-0.0400
STOP: 0.00 after surface 11.
DIA:
71.735
EFL: 319.279 FVD:
334.513
ENP:
4.50331
IMD: 10.0094 BRL:
324.504
OBD: -7995.69 OVL:
8330.21
SYSTEM FIRST ORDER PROPERTIES, POS 3
OBJ. HT:
-935.00 f/ 4.02 MAG:
-0.1600
STOP: 0.00 after surface 11.
DIA:
70.028
EFL: 365.941 FVD:
371.317
ENP:
60.0103
IMD: 9.99720 BRL:
361.319
OBD: -2251.24 OVL:
2622.56
__________________________________________________________________________
First Order Properties of Elements
Element Surface
Number Numbers Power f'
__________________________________________________________________________
1 1 2 0.48329E-02
206.92
2 3 4 -0.63507E-02
-157.46
3 5 6 0.11155E-02
896.44
4 7 8 0.66177E-02
151.11
5 9 10 -0.47302E-02
-211.41
6 12 13 0.34012E-02
294.01
__________________________________________________________________________
TABLE 3
__________________________________________________________________________
Surf. Clear Aperture
No. Type Radius Thickness Glass Diameter
__________________________________________________________________________
1 .infin.
5.00000 90.50
2 83.1719
13.00000 BACED5
91.00
3 233.9264
13.33000 89.11
4 -485.5457
6.47000 FD2 85.22
5 105.3363
25.75000 81.16
6 a 154.1888
10.00000 ACRYLIC
83.92
7 a 174.3731
2.00000 85.20
8 284.2298
14.70000 BACD5 87.00
9 -139.0179
Space 1 89.10
10 a -585.4332
11.69000 ACRYLIC
95.00
11 -164.0203
15.47000 95.50
12 a -131.3993
7.79000 ACRYLIC
96.00
13 a 452.6431
Space 2 108.00
14 Aperture stop
321.37000 82.70
15 .infin.
2.00000 ACRYLIC
304.00
16 acf -145.1760
Image distance 304.00
__________________________________________________________________________
Symbol Description
a -- Polynomial asphere
c -- Conic section
f -- Fresnel
__________________________________________________________________________
Conics
Surface
Number
Constant
__________________________________________________________________________
16 -1.0000E+00
__________________________________________________________________________
Even Polynomial Aspheres
Surf.
No.
D E F G H I
__________________________________________________________________________
6 -7.0450E-07
-1.4118E-11
-4.6437E-14
2.0991E-17
-8.3654E-21
1.8668E-24
7 -5.8899E-07
1.3633E-12
5.5836E-14
-8.2367E-17
3.4781E-20
-4.8293E-24
10 -4.2671E-08
2.3388E-10
-1.2627E-13
6.6272E-17
-2.3640E-20
3.6813E-24
12 -5.3253E-07
-1.0642E-10
3.9159E-14
-9.0601E-18
6.1443E-21
-1.7273E-24
13 -4.8337E-07
1.0322E-10
-3.0287E-14
1.7560E-17
-4.5633E-21
3.8509E-25
16 -2.9975E-09
1.1630E-14
-2.8304E-20
0.0000E+00
0.0000E+00
0.0000E+00
__________________________________________________________________________
Variable Spaces
Focus Space 1
Space 2 Focal
Image
Pos. T(9)
T(13) Shift
Distance
__________________________________________________________________________
1 5.227
-69.256 -1.432
9.957
2 5.227
-92.613 -0.642
9.990
3 5.227
-52.312 -1.787
9.935
4 14.700
-116.470 -1.285
9.997
5 0.777
-80.140 0.265
9.993
__________________________________________________________________________
SYSTEM FIRST ORDER PROPERTIES, POS 1
POS 1 System First Order Properties
OBJ. HT:
-1360.0 f/ 3.93 MAG:
-0.1100
STOP: 0.00 after surface 14.
DIA:
82.432
EFL: 363.715 FVD:
394.498
ENP:
37.2564
IMD: 9.95692 BRL:
384.541
OBD: -3229.58 OVL:
3624.07
SYSTEM FIRST ORDER PROPERTIES, POS 2
OBJ. HT:
-3750.0 f/ 3.93 MAG:
-0.0400
STOP: 0.00 after surface 14.
DIA:
82.572
EFL: 334.551 FVD:
371.174
ENP:
10.2225
IMD: 9.98978 BRL:
361.184
OBD: -8319.72 OVL:
8690.90
SYSTEM FIRST ORDER PROPERTIES, POS 3
OBJ. HT:
-935.00 f/ 4.15 MAG:
-0.1600
STOP: 0.00 after surface 14.
DIA:
77.947
EFL: 388.269 FVD:
411.420
ENP:
59.6933
IMD: 9.93544 BRL:
401.484
OBD: -2322.07 OVL:
2733.49
SYSTEM FIRST ORDER PROPERTIES, POS 4
OBJ. HT:
-3901.0 f/ 3.93 MAG:
-0.0384
STOP: 0.00 after surface 14.
DIA:
82.662
EFL: 320.597 FVD:
356.797
ENP:
-9.34592
IMD: 9.99721 BRL:
346.800
OBD: -8331.49 OVL:
8688.29
SYSTEM FIRST ORDER PROPERTIES, POS 5
OBJ. HT:
-3672.0 f/ 3.93 MAG:
-0.0409
STOP: 0.00 after surface 14.
DIA:
82.524
EFL: 342.287 FVD:
379.200
ENP:
21.0808
IMD: 9.99287 BRL:
369.207
OBD: -8312.39 OVL:
8691.59
__________________________________________________________________________
First Order Properties of Elements
Element Surface
Number Numbers Power f'
__________________________________________________________________________
1 2 3 0.53017E-02
188.62
2 4 5 -0.75677E-02
-132.14
3 6 7 0.43140E-03
2318.0
4 8 9 0.62533E-02
159.92
5 10 11 0.21869E-02
457.27
6 12 13 -0.48701E-02
-205.34
7 15 16 0.34012E-02
294.01
__________________________________________________________________________
TABLE 4
______________________________________
FIG. P.sub.0 P.sub.U1
P.sub.U2
P.sub.E3
P.sub.E4
______________________________________
1 0.0031 0.0061 -0.0049 0.0011
0.0066
2 0.0032 0.0061 -0.0047 0.0011
0.0066
3 0.0030 0.0047 -0.0025 0.0004
0.0063
______________________________________
Top